Wrist watch with a piezoelectric crystal as time-keeping oscillator

ABSTRACT

A wrist watch using a piezoelectric crystal as the time-keeping oscillator. The time-keeping oscillator has its output fed to a number of frequency divider stages so as to reduce the ultimate frequency to some low value, e.g., below 5 cps. By reducing the frequency to this low value, the moving device can directly engage the second-wheel thereby minimizing the size and friction losses in the wheel mechanism. Two exemplary moving devices are disclosed, one of which utilizes a rotating coil assembly which has a shift finger to engage the toothing on the second-wheel. The other disclosed example utilizes a driving fork fastened to the shaft of an oscillating magnetic system with the arms of the driving force engaging the toothing on the second wheel. The basic frequency divider also includes a number of various electronic circuits for reducing the width of the driving pulses so as to minimize power losses and maximize the effective battery life.

United States Patent Assmus et al.

[451 Sept. 26, 1972 [72] Inventors: Friedrich Assmus; Wolfgang Gunter;l-Ians Flaig, all of Schramberg-Sulgen, Germany [73] Assignee: GebruderJunghans GmbH,Schramberg, Germany [22] Filed: Nov. 14, 1969 [21] Appl.No.: 876,880

[30] Foreign Application Priority Data Nov. 15, 1968 Germany ..P 1809223.4

[52] US. Cl. ..58/23 TF, 318/129 [51 Int. Cl. ..G04c 3/02 [58] Field ofSearch ..58/23 AC, 23, 23 A, 23 TF, 58/23 V, 28, 28 A, 28 B; 310/95;3l8/l29 Primary Examiner-Richard B. Wilkinson Assistant Examiner-EdithC. Simmons Jackmon AnomeyBurns, Doane, Benedict, Swecker & Mathis [5 7ABSTRACT A wrist watch using a piezoelectric crystal as the timekeepingoscillator. The time-keeping oscillator has its output fed to a numberof frequency divider stages so as to reduce the ultimate frequency tosome low value, e.g., below 5 cps. By reducing the frequency to this lowvalue, the moving device can directly engage the second-wheel therebyminimizing the size and friction losses in the wheel mechanism. Twoexemplary moving devices are disclosed, one of which utilizes a rotatingcoil assembly which has a shift finger to engage the toothing on thesecond-wheel. The other disclosed example utilizes a driving forkfastened to the shaft of an oscillating magnetic system with the arms ofthe driving force engaging the toothing on the second wheel. The basicfrequency divider also includes a number of various electronic circuitsfor reducing the width of the driving pulses so as to minimize powerlosses and maximize the effective battery life.

22 Claims, 14 Drawing Figures PATENTEBsErzs Ian SHEET 1 [IF 5 wnlfganlgGamer BY Hans Fang INVENTORS Friedrich Assmus Afforne r PATENTEUserzs m23,693,343

sum 5 or 5 IN V EN TORS Friedrich Assmm Wolf an (unlrr Hans Fh lig WRISTWATCH WITH A PIEZOELECTRIC CRYSTAL AS TIME-KEEPING OSCILLATOR Theinvention relates to a wrist watch with a piezoelectric crystal astime-keeping oscillator; an oscillator circuit for the excitation of theoscillations in the piezoelectric crystal; several electronic frequencydivider stages; and a hand-moving device to which the output pulses ofthe frequency dividers are fed.

A quartz wrist watch is known (Retail Jeweller" of Feb. 28, 1968) inwhich a quartz crystal is employed for stabilizing a high-frequencyoscillator. The frequency of the output pulses of this oscillator isreduced by means of several electronic frequency divider stages to suchan extent that the pulses can be utilized to feed a motor which drivesthe hand mechanism. The electronic circuits are constructed asintegrated circuits.

In such watches numerous problems occur with relation to the maintenanceof high time-keeping accuracy over a longer period and under varyingenvironmental conditions. Thus it is difficult to construct theelectronic circuit, including the hand-moving mechanism, in such a waythat sufficiently low energy consumption is achieved so as to burden thebattery lodged in the small available space only to such an extent thatthe watch runs for a sufficiently long period of time. Besides, theoperation of the hand-moving mechanism meets with difficulties as aresult of the desired low energy consumption. That is, the operationbecomes increasingly difficult and subject to losses with an increase inthe drive pulse frequency, i.e., a decrease in the number of dividerstages. On the other hand, energy consumption increases with the numberof divider stages. The moving mechanism also poses a problem withrespect to the bearings. When a motor of relatively high rotationalspeed is employed, lubricated bearings are required. Furthermore, theenergy necessary for the motor drive should be small. If then, in duecourse of time, the oil thickens, the friction may increase to such anextent that the motive power no longer suffices to assure thesynchronous movement of the motor.

The invention aims at providing a piezoelectric wrist watch of very highaccuracy which, with a battery customary in trade, runs at least for ayear. Furthermore, variations in position or temperature, shocks and thelike, resulting from the various customs of the watch-wearers, shouldnot substantially impair the movement accuracy. With all this and uriderany prevailing conditions, a faultless drive should be assured.According to the invention this is accomplished by a combination of thefollowing characteristics;

a. Use of a piezoelectrically excited tuning fork;

b. Frequency division down to a frequency of below 5 cps;

0. Use of an electric circuit arrangement for narrowing the outputpulses of the frequency divider circuit;

d. Use of an electromagnetic step-by-step switch arrangement, to whichthe output pulses are fed, as the moving device;

e. The moving device engages the second-hand.

A piezoelectric crystal in the shape of a tuning fork and of specificdimensions has a relatively low natural frequency, so that an oscillatorof relatively low frequency can be used and the number of the subsequentfrequency divider stages can be kept small. The frequency division downto below 5 cps. requires, to be sure, a large number of frequencydivider stages.

This fact however, permits the employment of a moving device which forinstance engages the second-wheel directly, so that the wheel mechanismcan be so constructed that it occupies little space and its frictionlosses are relatively small.

By the use of frequency divider stages in the form of flip-flopcircuits, pulses are produced at the output of the divider circuit whosewidth equals that of the pulse interval. Since for the drive of themoving device only relatively brief pulses are necessary, energyconsumption is diminished by the narrowing of the pulses. Utilization ofan electromagnetic step-by-step switch mechanism as the moving deviceresults in a very reliable movement at low frequency. In this process,effects from a possible thickening of the lubricant are avoided, due tothe low speed of rotation. It is also possible to use entirely oil-freebearings.

An electromagnetic step-by-step switch arrangement, preferably amoving-coil arrangement is provided which consists for instance of acentrally located stationary permanent magnet core and a self-supportingcoil rotatable about the core, which coil bears a shift finger engagingthe second-wheel. In this structure the moment of inertia of therotatable part can be kept small, e.g., by using a moving coil ofaluminum wire, whereby energy consumption is kept small and a rapidmovement is assured.

The crystal tuning fork and the moving coil arrangement should bepositioned so that they are parallel to each other and theirlongitudinal axes are perpendicular to the hand shaft. The plane ofoscillation of the tuning fork should be perpendicular to the dial,whereby the effect of strong shocks is reduced.

Furthermore, as the electromagnetic step-by-step switch mechanism arotary magnet arrangement may be provided which may consist of afour-pole magnet arrangement with radially outward pointing magnetpoles, a stationary magnetic return which encloses the magnetarrangement while leaving the airgap, and a coil arrangement positionedin the airgap and acting upon the magnetic poles. The rotary magnetdevice supports preferably a driving fork engaging the secondwheel. Asthe switching arrangement for narrowing the output pulses of thefrequency divider circuit a flip-flop circuit may be provided which isswitched on by the last frequency divider stage and switched off by apreceding frequency divider stage. However, it is also feasible toprovide as switching arrangement for narrowing the output pulses of thefrequency divider circuit a NAND gate to which the pulses are fed fromthe last frequency divider stage and from several preceding frequencydivider stages. A reversing stage may be connected on the output side ofthe NAND gate.

The invention is subsequently explained in greater detail with the aidof the drawing by means of several embodiments. The drawing shows inFIG. 1, a rear view of a preferred embodiment of the invention with amoving-coil moving device partially in section along line I---[ of FIG.2;

in FIG. 2, an individual representation of the embodiment of FIG. I, insection, along line II-Il in FIG. I, on an enlarged scale;

in FIG. 3, an individual representation of the switch finger cooperatingwith the second-wheel, in perspective view and on an enlarged scale;

in FIG. 4, a modified embodiment with a rotary magnet moving devicepartially in section along line IV-IV of FIG. 5;

in FIG. 5, a partial illustration of the rotary magnet of FIG. 1 in asection along line V--V of FIG. 4',

in FIG. 6a a block diagram of an electronic circuit arrangement fornarrowing the output pulses of the frequency divider circuit withemployment of a flipflop circuit;

in FIG. 7, a graphic representation of the pulses produced by thecircuit of FIG. 6, namely a. control pulses ofa frequency of 8 cpss,

d. control pulses of a frequency of l cps and e. the output pulses ofthe flip-flop circuit;

in FIG. 8, a diagram of another circuit arrangement for narrowing theoutput pulses of the frequency divider circuit, with utilization of aNAND gate and of dividers;

in FIG. 9 and 10, further electronic circuit arrangements for narrowingthe output pulses of the frequency divider circuit, with employment ofNAND gates with transistors;

in FIG. 11, a circuit similar to that of FIG. 8 in which however, onlythree inputs are provided,

in FIG. 12, a circuit arrangement as in FIG. 11, however, in connectionwith a circuit for the self-starting of the moving device;

in FIG. 13, a modified switch arrangement for narrowing the outputpulses of the frequency divider circuit, with employment of a TTLNAND-gate, and

in FIG. 14, a graphic representation of the pulses produced, e.g., bymeans for the circuit of FIG. 11.

In FIG. 1, numeral 10 indicates the plate for the mechanism ofa wristwatch. 11 is the wheel mechanism bridge in which, among other things,the second-wheel 12 is supported. 13 indicates a support plate, fastenedto the case, for a piezoelectric tuning fork, preferably a quartz tuningfork 14 which is fastened to support plate 13.

Tuning fork 14 is excited into oscillation in any known manner by anelectric oscillator circuit. The pulses produced by the oscillatorcircuit are further fed to a frequency divider circuit which reduces thepulse frequency. A series connection of different flip-flop circuits ispreferably used as frequency divider circuit. A frequency of, e.g.,8,l92 cps., reduced by 13 divider stages to a frequency of preferably 1cps. may be used as pulse frequency for moving tuning fork 14. Theoutput pulses of the frequency divider circuit are suitably fed to acircuit for narrowing the output pulses. All electronic circuits arepreferably constructed in the form of integrated circuits. In the watchshown in FIG. 1 they are contained in bridge 15. Numeral 16 indicates aspace for lodging the battery which feeds the electronic circuit.

A moving coil arrangement, generally marked 17 is provided as the movingdevice. This moving coil arrangement contains a cylindrical permanentmagnet polarized in the direction of the diameter, as shown in FIG. 2.The magnetization is chosen in such a way that the moving coil ispositioned in the strongest magnetic field so as to reach highesteffectiveness. Core 30 is fastened by means of supports 26 and 27 toplate 10. A self-supporting coil 28 is arranged so as to enclose magnetcore 30 and is mounted rotatably in bearings 19 and 18 by means to axlejournals 20 and 2I. Return springs 22 and 23 are mounted on axlejournals 20 and 21. These return springs serve also for feeding thecurrent to coil 28 as well as or holding the coil or the shift finger 29in abutment against a setscrew 34 by means of which the position of restof coil 28 can be adjusted. Suitable supply lines are welded on at 24and 25. Furthermore, return metal sheets 31 and 32 are provided whichsurround coil 28 and keep the straying of the magnet system small.

Coil 28 may consist, e.g., of aluminum wire so that its moment ofinertia is as small as possible. The winding suitably takes place insuch a manner that oblong holes 33 are formed in the inactive coil sideswhich are located outside the magnetic field. Axle journals 20 and 21are inserted in these oblong holes 33 and can be fastened by glueing oralso by coating of the entire coil with a synthetic resin layer. Thismakes it possible to displace the axle journals laterally and thus toeffect a center of gravity compensation, particularly with respect tounilaterally mounted shift finger 29. The end of a spiral spring 23 canbe connected with the watch mechanism, whereas the end of the otherspiral spring is connected to the circuit contained in bridge 15. Atleast one of the bearings (in this case 19) must be insulated. In thisembodiment axle journal 20 runs on jewels of bearing 19.

A shift finger, generally marked 29, fastened to selfsupporting coil 28,engages the toothing of secondwheel 12 and effects the movement. Thisshift finger 29 is preferably fastened to coil 28 by glueing. Itconsists suitably of two parts 29a and 29b which may be glued to eachother. Each part 290 and 29b is provided with a driving surface 29c and29d which, when finger 29 moves, effect at each instance an advance ofthe second-wheel by half a tooth pitch. Second-wheel 12 is provided witha further toothing (locking tooth system) 36 whose pitch is half of thatof toothing 35. A retaining spring 37 engages locking tooth system 36 bymeans of a jewel 38 fastened to its free end. Retaining spring 37 isadjustable in its length by means of a rotatable post 39 and itsprestressing by means of a rotatable eccentric 40.

Movable coil arrangement 17 is elongated and of relatively smalldiameter. As a result of this and of the use of a self-supporting coilof aluminum wire the moments of inertia are very small so that the drivepower can be kept small. The moving coil arrangement, l.e.,self-supporting coil 28 performs only relatively short back and forthmovements so that employment of oilfree bearings becomes possible.

The moving coil is kept, when no current passes through it, by means ofhelical springs 22, 23 and shift finger 29 in such a position as to restagainst setscrew 34. When a current pulse passes through the coil it ismoved, in the embodiment of FIG. 2, in counterclockwise direction. Inthis process driving surface 29c moves second-hand 12 by half a toothpitch of moving toothing 35. After termination of the current pulse,coil 28 is returned by helical springs 22 and 23 to its position of restin which shaft finger 29 abuts against setscrew 34. In this processdriving surface 29d again advances second-wheel 12 by half a tooth pitchof toothing 35. The switching process takes place, e.g., with afrequency of l cps., whereas the switching itself takes only a fractionof a second.

Shift finger 29 and also second-wheel 12 may consist of plastic,beryllium or chromium-plated aluminum or aluminum provided with a hardeloxal coating. It is essential that the material has a sufficientabrasive resistance and is also relatively light. When plastic is usedit is of course not necessary that shift finger 29 consist of two parts.

In the embodiment of FIG. 4 and 5, numeral 50 indicates theclock-mechanism supporting plate. 51 is the watch mechanism bridge withsecond-wheel 52 whose toothing is marked 52a. 55 is the bridge whichcontains the electronic circuits and 56 the space for lodging theelectric battery. 53 is the support plate for quartz tuning fork 54mounted in support plate 53.

In the embodiment of FIG. 4, the electronic circuit may be the same asin the embodiment of FIG. 1. In the embodiment of FIG. 4, however,rotary magnet system 57 is provided as moving device. This magnet systemconsists of a stationary magnetic return 58 and a rotatable permanentmagnet arrangement 63-66 which is rotatable on a shaft 61. The permanentmagnet arrangement contains four permanent magnet poles 63-66. In theairgaps between magnet poles 63 to 66 and the magnetic return 58, twocoils 59 and 60 are arranged to which the output pulses of theelectronic divider circuit and the subsequent circuit for the narrowingof the drive pulses are fed. In this case a movable supply to the coilsis not required.

A driving fork 68 is fastened to shaft 61 of the magnet system. The arms68a and 68b of this driving fork support pins 69a and 69b which engagetoothing 52a of second-hand 52 and effect the movement thereof.

The return elements 58 consist of ferromagnetic material whereas thesupport element 62 need not be ferromagnetic and consists thereforesuitably of as light a material as possible, e.g., of aluminum orplastic. The driving fork 68 may consist of such material. Secondwheel52 is suitably made of one of the materials mentioned in connection withFIG. 1.

FIG. 4 shows driving fork 68 in the position of rest. When a currentpulse passes through coils 59 and 60, magnet system 61 and 66 is movedin counterclockwise direction. In this process fork pin 69a advancessecondwheel 52 by half a tooth pitch. After the termination of thecurrent pulse, driving fork 68 is returned by the restoring force of themagnet system in cooperation with return element 58 to the position ofrest shown in FIG. 4, in which process the fork pin 69b moves thesecond-wheel by another half tooth pitch. The restoring force isproduced by the fact that return element 58 is not a closed ring butopen on one side.

Return element 58 is suitably rotatable. By means of an eccentric 70,return element 58 can be turned and thereby the position of rest ofdriving fork 68 can be adjusted.

In the embodiments of FIGS. 1 and 4, the oscillation plane of tuningfork 14, 54 is perpendicular to the dial of the watch. By this device,an inadmissibly strong stress of the tuning fork by shock due to an armmovement in the direction of maximum acceleration is largely avoided.

FIGS. 6 to 14 show circuits for narrowing the output pulses of thefrequency divider circuit. In the circuit of FIG. 6, AB, C, D, indicate,for example, some frequency divider stages. The pulses supplied from thefrequency divider circuit are symmetrical pulses of equal polarity whichmay control, e.g., an amplifier for the drive of a moving device. Thisamplifier supplies then at the output side pulses of a polarity in whichthe ratio between pulse duration and pulse interval equals 1. Thishowever, means that during half a period of movement of the moveddriving system a drive current flows, although the coil of the movingdevice is located only during a part of this period in the magneticfield of the magnet system. Temporarily, therefore, there flows adriving current of no, or only small, effect upon the moved system, sothat an unfavorable effect results.

In FIG. 6, E indicates a pulse former which, like the frequency dividerstages A to D, may be, e.g., a flip-flop circuit, connected at the inputside to the last frequency divider stage D and a further frequencydivider stage. In this process the pulse-forming stage E is switched onby the last frequency divider stage and switched off by the otherconnected frequency divider stage. When in the embodiment shown, thelast frequency divider stage D furnishes a pulse frequency of l cps. (din FIG. 7), frequency divider stage A supplies a pulse frequency of 8cps. (a in FIG. 7). This setup produces at the output of pulse-formingstage E pulses of a frequency of 1 cps. and a pulse duration of 62.5milliseconds (e in FIG. 7). When pulse-forming stage E is connected tostage A, e.g., to the 64 cps. stage, output pulses of a pulse durationof, e.g., only 7.8 milliseconds are obtained, which is readily achievedby means of the circuit shown. This pulse period of 7.8 milliseconds,proved favorable with a pulse frequency of l cps.

In place of the pulse-forming stage according to FIG. 6, a NAND gateofknown type (of, e. g., periodical Elektronik,"No. 10/1968, Arbeitsblatt(Work Gazette) No. 20 Integrated digital circuits) can be used which isfed from the last frequency stage and from several preceding dividerstages. In this process the last frequency divider stage determines thepulse frequency whereas the frequency divider stage of highest frequencydetermines the width of the pulse. The frequency dividers may be, e.g.,a chain of bistable elements.

FIG. 8 shows a circuit with a four input NAND gate with diodes D1 to D4,transistor Tr l with working resistance RI and reversing stage withtransistor Tr 2 and coil L which may be, e.g., coil 28 of FIG. 1 or coil59, of FIG. 4.

FIG. 9 shows another embodiment of a NAND gate with a transistor Tr 3 inwhose exciting circuit transistors Tr 4 to Tr 7 are series-connected. R2to R 6 are series resistors. In this circuit a current flows in coil Lwhen all transistors Tr 4 to Tr 7 are conducting.

In the circuit of FIG. 10, on the other hand, transistors Tr 9 to Tr 12are connected in parallel in the input circuit of a transistor Tr 8. Inthis set-up a current flows in coil L only when none of the transistorsTr 9 to Tr 12 is conducting.

FIG. 11 shows a circuit with three-input NAND gate with transistor Trl3, diodes D 5 to D 7 and working resistor R 8. A reversing stage with atransistor Tr 14, which feeds coil L, in series-connected to the gatevia a resistor R 9.

FIG. 12 shows a corresponding circuit for an automatically controlledsystem with one transistor stage Tr 15, a control coil L and a drivecoil LA. R 12 is an adjustable resistor. In this case the moving coilmay consist of three partial windings L, L,,, LA. When the coil moves.voltage pulses are induced in control winding L which pulses after beingamplified by transistor Tr l and flow through a drive winding LA anddrive the moving coil. These windings L and LA in cooperation with thecorresponding connection and transistor Tr l5 permit an automatic startof the moving device. Winding L through which the output pulses of thefrequency divider stages flow, effects a synchronization of the movingcoil to the desired frequency derived from the piezoelectric crystal.

FIG. 13 finally shows a circuit with a TTL'NAND gate with a transistorTr 16 with several emitter electrodes and a reversing stage, connectedas the output side, and with transistor Tr 17 which feeds coil L.

FIG. 14 shows a graphic representation of the pulses which occur. e.g.,in connection with the circuit of H6. 11. Letter a indicates the outputpulses of the frequency divider stage with 16 cps; b the output pulsesof the frequency divider stage with 8 cps., and c the output pulses ofthe frequency divider stage with 4 cps; d are voltage pulses at thecollector of transistor Tr 13, e are the voltage pulses at the collectorof transistor Tr 14, and f the voltage pulses at the collector oftransistor Tr 14 with superposed voltage pulses when the movingmechanism moves.

The circuits for narrowing the output pulses of the frequency dividercircuit according to FIGS. 6 to 14 are usable not only for watches withmoving coil arrangement engaging the second-wheel or rotary magnetarrangement, but also for watches in which the hand mechanism is drivenby a moving device with a balance wheel oscillator or by a motor, andalso for watches in which drive pulses with a frequency of more than 5cps.

occur.

What is claimed is:

l. A wrist watch drive mechanism comprising:

a tuning fork piezoelectric crystal element operable to produce outputelectrical pulses;

frequency division means electrically connected to said tuning forkpiezoelectric crystal element for dividing the frequency of the outputelectrical pul ses;

a second wheel; and,

electromagnetic drive means including a moving coil arrangementconnected to said frequency division means and said second wheel forrotating said second wheel in response to electrical pulses from saidfrequency division means,

said moving coil arrangement comprising a centrally located, stationarypermanent magnet core, a coil rotatable about the core, and a shiftfinger directly engaging the second wheel and supported by said coil.

2. A wrist watch drive mechanism as defined in claim 1, wherein theshift finger consists of two parts each of which is provided with adriving surface which advances the second-wheel by half a tooth pitch.

3. A wrist watch drive mechanism as defined in claim 1, wherein theshift finger is glued to a moving coil.

4. A wrist watch drive mechanism as defined in claim I, and furthercomprising; an adjustable stop positioned beneath said shift fingeragainst which the coil is made to rest by return springs.

S. A wrist watch drive mechanism as defined in claim 1 wherein themoving coil consists of aluminum wire.

6. A wrist watch drive mechanism as defined in claim I, wherein the endsof the moving coil are conductively connected to insulated axlejournals.

7. A wrist watch drive mechanism as defined in claim 6, wherein saidcoil has inactive sides and including oblong holes for receiving theaxle journals parallel to the coil wires.

8. A wrist watch drive mechanism as defined in claim 7, wherein the axlejournals are glued into the oblong holes.

9. A wrist watch drive mechanism as defined in claim 7, wherein the axlejournals are fastened to the oblong holes by spraying synthetic resinaround the coil.

10. A wrist watch drive mechanism as defined in claim 1, wherein amagnetic return element surrounding the coil is provided.

11. A wrist watch drive mechanism as defined in claim 1, wherein saidshift finger is fashioned from a material of low specific weight andsufficient abrasive resistance.

12. A wrist watch drive mechanism as defined in claim 1, wherein saidtuning fork and said moving coil arrangement are essentially parallel toeach other and their longitudinal axes are parallel with saidsecondwheel.

13. A wrist watch drive mechanism comprising:

a. a tuning fork piezoelectric crystal element operable to produceoutput electrical pulses;

b. frequency division means electrically connected to said tuning forkpiezoelectric crystal element for dividing the frequency of the outputelectrical pulses',

c. a second wheel;

d. electromagnetic drive means connected to said frequency divisionmeans and said second wheel for rotating said second wheel in responseto electrical pulses from said frequency division means; and,

e. means connected between said frequency division means and saidelectromagnetic drive means for narrowing the output pulses of saidfrequency division means.

14. A wrist watch drive mechanism as defined in claim 13, wherein theoscillating plane of the tuning fork is perpendicular to the saidsecond-wheel.

15. A wrist watch drive mechanism as defined in claim 13 wherein saidelectromagnetic drive means includes:

a movable magnet arrangement.

16. A wrist watch drive mechanism as defined in claim 15, wherein saidmovable magnet arrangement comprises a four-pole magnet device withmagnet poles pointing outward in radial direction, a stationary magneticreturn surrounding the magnetic device while leaving an airgap, and acoil arrangement mounted in the airgap and energizing the magnet poles.

17. A wrist watch drive mechanism as defined in claim 16, wherein saidmagnet device supports a driving fork which directly engages saidsecond-wheel.

18. A wrist watch drive mechanism as defined in claim 16, wherein saidmagnet return for producing a return force which acts upon the rotarymagnet device comprises: a partly open ring.

19. A wrist watch drive mechanism as defined in claim 18, wherein saidopen ring which forms the return is rotatable for the purpose ofadjustment of the position of rest of the rotary magnet arrangement.

20. A wrist watch drive mechanism as defined in claim 13, wherein saidfrequency division means comprises a plurality of stages and said meansfor narrowing the output pulses of said frequency divider meanscomprises: a flip-flop circuit turned on by a last frequency dividerstage and turned off by a preceding frequency divider stage.

1. A wrist watch drive mechanism comprising: a tuning fork piezoelectriccrystal element operable to produce output electrical pulses; frequencydivision means electrically connected to said tuning fork piezoelectriccrystal element for dividing the frequency of the output electricalpulses; a second wheel; and, electromagnetic drive means including amoving coil arrangement connected to said frequency division means andsaid second wheel for rotating said second wheel in response toelectrical pulses from said frequency division means, said moving coilarrangement comprising a centrally located, stationary permanent magnetcore, a coil rotatable about the core, and a shift finger directlyengaging the second wheel and supported by said coil.
 2. A wrist watchdrive mechanism as defined in claim 1, wherein the shift finger consistsof two parts each of which is provided with a driving surface whichadvances the second-wheel by half a tooth pitch.
 3. A wrist watch drivemechanism as defined in claim 1, wherein the shift finger is glued to amoving coil.
 4. A wrist watch drive mechanism as defined in claim 1, andfurther comprising; an adjustable stop positioned beneath said shiftfinger against which the coil is made to rest by return springs.
 5. Awrist watch drive mechanism as defined in claim 1, wherein the movingcoil consists of aluminum wire.
 6. A wrist watch drive mechanism asdefined in claim 1, wherein the ends of the moving coil are conductivelyconnected to insulated axle journals.
 7. A wrist watch drive mechanismas defined in claim 6, wherein said coil has inactive sides andincluding oblong holes for receiving the axle journals parallel to thecoil wires.
 8. A wrist watch drive mechanism as defined in claim 7,wherein the axle journals are glued into the oblong holes.
 9. A wristwatch drive mechanism as defined in claim 7, wherein the axle journalsare fastened to the oblong holes by spraying synthetic resin around thecoil.
 10. A wrist watch drive mechanism as defined in claim 1, wherein amagnetic return element surrounding the coil is provided.
 11. A wristwatch drive mechanism as defined in claim 1, wherein said shift fingeris fashioned from a material of low specific weight and sufficientabrasive resistance.
 12. A wrist watch drive mechanism as defined inclaim 1, wherein said tuning fork and said moving coil arrangement areessentially parallel to each other and their longitudinal axes areparallel with said second-wheel.
 13. A wrist watch drive mechanismcomprising: a. a tuning fork piezoelectric crystal element operable toproduce output electrical pulses; b. frequency division meanselectrically connected to said tuning fork piezoelectric crystal elementfor dividing the frequency of the output electrical pulses; c. a secondwheel; d. electromagnetic drive means connected to said frequencydivision means and said second wheel for rotating said second wheel inresponse to electrical pulses from said frequency division means; and,e. means connected between said frequency division means and saidelectromagnetic drive means for narrowing the output pulses of saidfrequency division means.
 14. A wrist watch drive mechanism as definedin claim 13, wherein the oscillating plane of the tuning fork isperpendicular to the said second-wheel.
 15. A wrist watch drivemechanism as defined in claim 13 wherein said electromagnetic drivemeans includes: a movable magnet arrangement.
 16. A wrist watch drivemechanism as defined in claim 15, wherein said movable magnetarrangement comprises a four-pole magnet device with magnet polespointing outward in radial direction, a stationary magnetic returnsurrounding the magnetic device while leaving an airgap, and a coilarrangement mounted in the airgap and energizing the magnet poles.
 17. Awrist watch drive mechanism as defined in claim 16, wherein said magnetdevice supports a driving fork which directly engages said second-wheel.18. A wrist watch drive mechanism as defined in claim 16, wherein saidmagnet return for producing a return force which acts upon the rotarymagnet device comprises: a partly open ring.
 19. A wrist watch drivemechanism as defined in claim 18, wherein said open ring which forms thereturn is rotatable for the purpose of adjustment of the position ofrest of the rotary magnet arrangement.
 20. A wrist watch drive mechanismas defined in claim 13, wherein said frequency division means comprisesa plurality of stages and said means for narrowing the output pulses ofsaid frequency divider means comprises: a flip-flop circuit turned on bya last frequency divider stage and turned off by a preceding frequencydivider stage.
 21. A wrist watch drive mechanism as defined in claim 13,wherein said frequency division means comprises a plurality of stagesand said means for narrowing the output pulses of the frequency dividermeans comprises: a NAND gate to which current is fed from a lastfrequency divider stage as well as from several preceding frequencydivider stages.
 22. A wrist watch drive mechanism as defined in claim21, and further comprising: a reversing stage connected to the outputside of the NAND gate.